1. Field of the Invention
The present invention relates to an optical disc device that records information on a recordable optical disc having a power calibration area (PCA) for optimum recording power control.
2. Description of the Related Art
An optical disc for recording such as a DVD (Digital Versatile Disc)-R (Recordable) or a DVD-RW (Rewritable) has a trial recording or writing area (power calibration area which is hereinafter referred to as PCA). An optimum recording power can be detected by performing a trial recording in the PCA with different powers of a laser beam, and then reproducing the recorded data. In a rewritable optical disc such as a DVD-RW, trial writing data in the PCA can be erased. If repetitious optimum recording power control leads to depletion of free space (unused area) for further trial recording, the trial writing data in the PCA can be erased to create free space, preventing the optimum recording power control from being impossible. On the other hand, in a recordable optical disc such as a DVD-R (of the type which cannot erase the recorded data and write new data there), trial writing data recorded in the PCA cannot be erased, and hence the number of available times of optimum recording power control has an upper limit (normally about 100 times).
Since once recorded trial rewriting data cannot be erased in a recordable optical disc as described above, a variety of technologies for effectively utilizing a limited amount of a PCA by reducing the amount of the PCA used for one optimum recording power control are being developed. For example, the following technology is known with regard to a CD-R (Compact Disc-Recordable). That is, without simply changing a laser power during trial writing by 15-stage, the operation of a β value is performed from a reproduction result of a trial writing with an initially set laser power, and the most desirable value is selected from the 15-stage as the next trial writing laser power, so that the amount of a PCA required for one optimum recording power control can be reduced to a large extent (see Japanese Laid-Open Patent Publication No. 11-353686).
Further, the following technology is also known with regard to a CD-R. That is, first, a trial writing is performed with a five-stage laser power based on a recommended recording power and, from their respective reproduction results, a five-stage laser power of a narrower width is set. And then a recording power can be determined finally from a trial writing result with the laser power so set, thereby saving the amount of a PCA required for one optimum recording power control (see Japanese Patent No. 3534628).
As stated above, in recordable optical discs such as a CD-R and a DVD-R, like a recording area, a PCA for optimum recording power control is used up (not rewritable). Therefore, a variety of technologies for saving the amount of a PCA used for one optimum recording power control are being developed in order that a limited PCA enables a larger number of times of an optimum recording power control. In the recordable optical discs, however, the following problem may arise in performing a finalizing process after recording predetermined information.
The term “finalizing process” means a process in which a lead-in and a lead-out that indicate a range of item information of recorded contents and a range of information recording area, and the like are recorded in an optical disc after being subjected to information recording, so that the optical disc can be reproduced with other optical disc device. However, when environmental conditions within an optical disc device are changed, for example, the ambient temperature of an optical pickup reaches or exceeds a predetermined temperature during the execution of a finalizing process, the optical disc device spontaneously performs an optimum recording power control to maintain recording quality. Therefore, if the amount of an unused area remaining in a PCA is small at the time of starting a finalizing process, there may arise such a trouble that the necessary optimum recording power control cannot be performed in the middle of the finalizing process, failing to complete the finalizing process. In this case, this optical disc is not finalized, resulting in such a faulty optical disc that cannot be reproduced with other optical disc device.
In a CD-R, a PCA area for one optimum recording power control during finalizing process is to be reserved (for example, the paragraph “0005” of Japanese Patent No. 3534628). Specifically, a CD-R has a counter area for managing the number of times a PCA is used, and hence an optical disc device can recognize the utilization circumstances of the PCA only by referring to the counter area. This permits reservation of an area required for performing just one optimum recording power control, so that the above-mentioned disadvantage can be avoided relatively easily. On the other hand, in a DVD-R, there is no counter area for indicating the number of times a PCA is used, and only a head address of trial writing data written in the PCA is recorded. It is therefore not easy to accurately recognize the amount of an unused area remaining in the PCA at a proper time, making it difficult to prevent occurrence of the above-mentioned trouble. Furthermore, the DVD-R has more process items during finalizing process (information that should be recorded additionally in an optical disc) than the CD-R, and the shift amount of an optical pickup extends to a wide range of the optical disk. As a result, the amount of the PCA required for optimum recording power control during finalizing process is indefinite, in this respect, (even though the DVD-R can manage the number of times the PCA is used by means of the same counter area as in the CD-R), it is difficult to prevent occurrence of the above-mentioned trouble.